Note that what this code does is first convert the String to a charcter array, then adds their ASCII codes together, meaning that a = 97, while b = 98, b > a. You are going to get problems when it comes to capitals though, since a = 97, while CAPITAL B = 66 making it a > B. One solution is to just convert everything to lowercase before you check it. The other one is a little more complicated, it involves changing the for loops:

What this does is simple:
It evaluates the character, if the character value is greater than 54 (so we cover in case there are numbers in the string, 1-9 or other chars) but less then 90, we assume that the value is a capital letter. Then we add to the size the value of the letter + 64, (twice the difference between the lowercase characters, and the uppercase characters).